The present disclosure relates to a gear apparatus for a centrifuge, such as a solid bowl screw centrifuge. The solid bowl screw centrifuge includes a drum to be driven and a screw to be driven at a differential rotational speed relative to the drum. The gear apparatus is connected between at least one or more drive motors and the screw and the drum and the gear apparatus is continuously filled with an oil-type free-flowing lubricant.
For driving decanters, for example, solid bowl screw centrifuges, use is made of gear apparatuses which are connected downstream of the drive motors and have elements which rotate at the rotational speed of the drum.
In decanter gear apparatuses which are continuously filled with oil, it is not readily possible to check the filling level or add more gear oil during ongoing operation. Leaks, for example toward the product space, can be detected only when the apparatus is stationary during maintenance work. In addition, in the decanter of the type in question, an elevated pressure can build up in the gear. It is desirable to avoid this.
With regard to the technological background, reference is made to WO 2004/097255 A2, DE 19 18 130 A, DE 20 2005 001 539 U1, DE 103 34 370 A1, EP 0 409 791 B1, DE 1 009 865 A1 and DE 1 782 548 A.
Against the background of the problem described above, the gear apparatus, according to the present disclosure, addresses this problem.
Thus, the present disclosure relates to a gear apparatus for a solid-bowl screw centrifuge. The centrifuge includes a drum and a screw, both of which drum and screw are configured to be driven and the screw is further configured to be driven at a different rotational speed relative to the drum. The gear apparatus is connected between one or more drive motors and the screw and the drum. The gear apparatus is continuously filled with a lubricant and includes a hollow drive shaft having at least one hollow channel. An associated lubricant compensating system includes a lubricant compensating container. The lubricant compensating container is connected via a line to the at least one hollow channel.
Accordingly, as noted above, the gear apparatus has associated with it a lubricant compensating system, in particular a lubricant compensating circuit, with a lubricant compensating container which is connected via a line to at least one hollow channel of a drive shaft of the gear apparatus. The drive shaft is embodied as a hollow shaft.
In order to compensate for any losses of oil and in order to promptly obtain during operation an indication of an existing leak, an oil compensating container is installed above the gear apparatus. The oil compensating container is connected to the oil volume in the gear via a rotary lead-in, the transfer point being located axially and centrally on the drive shaft of the gear. If oil is lost in the gear, oil can run out of the container into the gear. Damage is thus prevented in a simple manner.
In addition, the gear apparatus of the present disclosure avoids differences in pressure or prevents pressure from building up in the gear apparatus during heating in a manner that might lead to “breathing” and possibly the infiltration of dirt/water.
In addition, oil losses become more reliably detectable. It is thus possible to visually detect a loss of oil before the gear apparatus is jeopardized.
In addition, possible contamination of the material to be centrifuged is impeded, particularly in the case of an internal gear.
In addition, it is possible to add more oil into the gear apparatus during ongoing operation if production has to be maintained.
Nevertheless, in an implementation of a drive concept with motors mounted on the end side and coaxially with the drive shaft, referred to as a direct drive, the concept of the central rotary lead-in is possible only with relatively great technical effort. However, motors with a hollow shaft can be used, the hollow shaft being an advantageous element according to the present disclosure.
If the rotary lead-in is positioned in such a way that it surrounds the hollow drive shaft, the oil has to enter the hollow shaft via a hole in the lateral surface. It is within the scope of the present disclosure to form this hole radially and thus to encounter a hole or line in the center of the shaft that then leads to the gear apparatus volume.
Nevertheless, when the gear housing is stationary, the rotating drive shaft attempts to pump oil out of the gear apparatus into the compensating container, since the oil is outwardly accelerated in the radial hole of the shaft. If the suction is sufficiently high, oil flows out and air is drawn into the gear apparatus under the dynamic seals. It is possible to avoid this effect if an equivalent radial hole is arranged at the inner end of the drive shaft.
A further problem exists in the fact that it is not possible to reliably rule out loss of oil in the gear apparatus. If, for example, the gear apparatus contains a relatively large air bubble, then the holes in the drive shaft are empty and the oil would have to enter the shaft from the outside counter to the centrifugal force.
In order to achieve reflowing of the oil, the oil would have to be pressurized in a controlled manner in the container. This is impracticable.
These further problems can be solved by the gear apparatus, according to the present disclosure, by providing a drive shaft which is designed as a hollow shaft and has two axially extending oil holes which, according to an embodiment of the present disclosure, are drilled eccentrically and obtain transverse holes positioned next to one another. It is also within the scope of the present disclosure to form one of the oil holes centrically and the other eccentrically or, for example, coaxially with the first oil hole.
The transverse holes are drilled onto the longitudinal holes so as to be laterally offset and oblique relative to one another, such as in accordance with the peeling disk principle.
It is advantageous if the transverse holes are formed independently of the direction of rotation in such a way that one channel pumps and one draws in. When the housing rotates, a correspondingly designed rotary lead-through provides a defined system. That is, oil is conveyed into the gear apparatus in a targeted manner and air is conveyed out. This arrangement has a plurality of advantages.
To begin with, it is operative independently of the direction of rotation.
In addition, it allows air to be brought safely out of the gear apparatus.
In addition, the solution, according to the present disclosure, can be implemented in a simple manner in designs having a secondary motor arranged on the end side for driving the screw. It is particularly suitable for lubricating the gear apparatus with oil instead of fat.
If the two channels in the rotary lead-through are uncoupled from each other by an intermediate seal and connected via two hoses, a passage and cooling are also conceivable within the scope of the present disclosure.
Embodiments of the present disclosure are further discussed below.
Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.